September in Waterbury averages a daily high of 24.6°C with nights around 12.4°C. Expect roughly 11.2 wet days totalling 117.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Waterbury is August–October.
Based on MERIDEN MARKHAM MUNICIPAL AIRPORT, CT US (19.4km), 1995–2024. 25 years of September data.